In work with recombinant DNA-containing microorganisms, waste material containing not only living organisms but also active nucleic acids are produced. This waste material must be inactivated in accordance with the respective safety requirements before the biomass can be passed to a purification plant.
Although many microorganisms and cell cultures can be killed by heating at 80.degree. C., the DNA is not destroyed by such treatment. That is, vital cell functions such as respiration or photosynthesis may cease. However, nuclear material such as DNA or RNA may remain intact.
The known methods recognized by the Central Commission of Biological Safety (ZKBS) of the Federal Republic of Germany, for sterilization and cell inactivation (e.g. steam sterilization for 20 minutes at 121.degree. C.) are very expensive. When used on an industrial scale, the recognized methods are cost intensive and may be impractical.
In these ZKBS-approved disposal processes, the DNA is degraded to units shorter than 500 base pairs. Units of this size are no longer biologically active and can be transferred into waste water without giving rise to any risks.
Generally, inactivation of cell biomass or cellular material must be carried out before being fed to the purification plant. Thus, it is of primary concern that substances used in inactivation procedures not be harmful or fatal to microorganisms. It is particularly important that such substances not be harmful to microorganisms commonly associated with the activated sludge purification process.
It is, moreover, desirable that the substance used is nontoxic or that it can be rendered harmless by being degraded by microorganisms such as bacteria present in an activated sludge process. It is also desirable that the inactivating substances have no negative influence on the walls and other surfaces of the fermentation and purification equipment. Preferably, such substances would have relatively minimal corrosive or erosive characteristics.
German Patent Application DE 05 37 33 921 describes a process for inactivating DNA, in particular recombinant DNA, wherein a percarboxylic acid with 1 to 3 carbon atoms or a salt thereof, an alkali peroxide or an alkali peroxomonosulfate is added to a DNA-containing biomass. The mixture is then heated at 60.degree. to 100.degree. C. for 20 to 60 minutes, preferably at pH 6 to 11. The percarboxylic acids, e.g. peroxyacetic acid, are, however, relatively unstable.
It is also known that a DNA chain when heated for 40 minutes at 100.degree. C. in a phenol-containing saline solution is extensively degraded (Meth. Enzymol. B XII, page 97).
In another known process, Meth. Enzymol A XII, pages 222-223 describes the degradation of DNA to produce apurinic acid using 98% formic acid at 30.degree. C. for 17 hours.